what is the sum of the digits of 111111x111111?

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I have just learnt that there are palindromic numbers that are formed by multiplying for instance 11x11=121, 111x111=12321 but I having difficulties getting the meaning of the question. Any assistance on how to answer this question will be highly appreciated?

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1 Answer

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The simple way is to type it into a calculator. The more clever way is to note that there are $6 \cdot 6=36$ pairs of $1$'s and when you do the addition part of the long multiply there are no carries.

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